Characterization of a Roller Seismic Isolation Bearing with Supplemental Energy Dissipation for Highway Bridges

A new roller seismic isolation bearing is developed for use in highway bridges. This new bearing uses rolling of cylindrical rollers on V-shaped sloping surfaces to achieve seismic isolation. The bearing is characterized by a constant spectral acceleration under horizontal ground motions and by a self-centering capability, which are two desirable properties for seismic applications. The former makes resonance less likely to occur between the bearing and horizontal earthquakes, while the latter guarantees that the bridge superstructure can self-center to its original position after earthquakes. To provide supplemental energy dissipation to reduce the seismic responses, the bearing is designed with a built-in sliding friction mechanism. This paper presents the seismic behavior of the bearing through analytical and experimental studies. First, the acceleration responses of and forces acting on the bearing under base excitation are presented. Next, the governing equation of horizontal motion, the base shear-horizontal displacement relationship, and conditions for self-centering, for the rollers to maintain contact with the bearing plates, and for rolling without sliding are discussed. An experimental study on a prototype bearing was carried out to verify and calibrate its characteristics and the results are discussed.